System for Assisting Rescuers in Performing Cardio-Pulmonary Resuscitation (CPR) on a Patient

ABSTRACT

A system for assisting a rescuer in performing cardio-pulmonary resuscitation (CPR) on a patient includes: a proximity sensor configured to be positioned at a location corresponding to a location of a rescuer&#39;s hand when delivering compressions to a patient&#39;s chest, the proximity sensor configured to produce a signal indicative of the rescuer&#39;s hands being released from the patient&#39;s chest; a medical device operatively coupled with the proximity sensor and configured to provide resuscitative treatment to the patient; and a controller communicatively coupled with the medical device and the proximity sensor. The controller is configured to: determine, based upon the signal from the proximity sensor, if the rescuer&#39;s hands have been released from the patient&#39;s chest, and trigger an action by the medical device in response to a determination that the rescuer&#39;s hands have been released from the patient&#39;s chest.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 15/601,465, filed May 22, 2017, which is continuation of U.S.patent application Ser. No. 15/178,578, filed Jun. 10, 2016, now U.S.Pat. No. 9,682,009, which is a continuation of U.S. patent applicationSer. No. 14/605,653, filed Jan. 26, 2015, now U.S. Pat. No. 9,387,147,which is a continuation of U.S. patent application Ser. No. 14/107,066,filed Dec. 16, 2013, now U.S. Pat. No. 8,979,764, which is acontinuation of U.S. patent application Ser. No. 13/555,439 filed onJul. 23, 2012, now U.S. Pat. No. 8,634,937, which claims priority toU.S. Provisional Application No. 61/527,663 filed Aug. 26, 2011, each ofwhich is incorporated by reference herein in its entirety. Thisapplication is also a continuation-in-part of U.S. patent applicationSer. No. 15/175,500, filed Jun. 7, 2016, which is a continuation of U.S.patent application Ser. No. 14/299,092 filed Jun. 9, 2014, now U.S. Pat.No. 9,364,680, which is a continuation of U.S. patent application Ser.No. 13/398,280 filed Feb. 16, 2012, now U.S. Pat. No. 8,781,577, whichclaims benefit of priority to U.S. Provisional Application Ser. No.61/473,273, filed Apr. 8, 2011, each of which is incorporated byreference herein in its entirety.

BACKGROUND Field of the Invention

This document relates to cardiac resuscitation, and in particular tosystems and techniques for assisting rescuers in performingcardio-pulmonary resuscitation (CPR) and other resuscitative activities.

Description of Related Art

The heart relies on an organized sequence of electrical impulses to beateffectively. Deviations from this normal sequence is known asarrhythmia. Certain medical devices include signal processing softwarethat analyzes electrocardiography (ECG) signals acquired from a medicalpatient (e.g., a victim at a scene of an emergency) to determine when acardiac arrhythmia such as ventricular fibrillation (VF) or shockableventricular tachycardia (VT) exists. These devices include automatedexternal defibrillators (AEDs), ECG rhythm classifiers, and ventriculararrhythmia detectors. An AED is a defibrillator—a device that deliverscontrolled electrical shock to a patient—while being relatively easy touse, such as by providing verbal prompts to a provider of care to “talk”the provider through a process of evaluating a patient for, attachingthe patient to, and activating, AED therapy. Certain of the medicaldevices just discussed are also capable of recognizing different cardiacwaveforms such normal sinus rhythm, aystole, VT and VF.

Many AEDs implement algorithms to recognize the VT and VF waveforms byperforming ECG analyses at specific times during a rescue event of apatient using defibrillation and cardio-pulmonary resuscitation (CPR).The first ECG analysis is usually initiated within a few seconds afterthe defibrillation electrodes are attached to the patient. Typically, ifthe ECG analysis detects a shockable rhythm, the rescuer is advised todeliver a defibrillation shock.

Following the defibrillator shock delivery or when any of the analysesdescribed above detects a non-shockable rhythm, treatment protocolsrecommended by the American Heart Association and European ResuscitationCouncil require performing CPR on the victim for a period of twominutes. The CPR includes rescue breathing and chest compressions.Following this period of CPR, the AED reinitiates ECG analysis asdescribed above. The sequence of one ECG analysis/defibrillation shockfollowed by 2 minutes of CPR continues in a repetitive fashion for aslong as the AED's power is turned on and the patient is connected to theAED device. Typically, the AED provides audio prompts to inform therescuer when analyses are about to begin, what the analysis resultswere, and when to start and stop the delivery of CPR.

Many studies have reported that the discontinuation of precordialcompression can significantly reduce the recovery rate of spontaneouscirculation and 24-hour survival rate for victims. Thus, it is useful torecognize abnormal heart rhythms during chest compressions. There isrecent clinical evidence showing that performing chest compressionsbefore defibrillating the patient under some circumstances can bebeneficial. Specifically, it is clinically beneficial to treat a patientwith chest compressions before defibrillation if the response times ofthe medical emergency system result in a delay of more than fourminutes, such that the patient is in cardiac arrest for more than fourminutes. Chest compression artifact rejection can employ spectralanalysis of the ECG, defibrillation success prediction, and therapeuticdecision-making typically specify a set of parameters in the ECGfrequency spectrum to be detected. For example, U.S. Pat. No. 5,683,424compares a centroid or a median frequency or a peak power frequency froma calculated frequency spectrum of the ECG to thresholds to determine ifa defibrillating shock is necessary.

SUMMARY

In some aspects, a method for providing adaptive CardiopulmonaryResuscitation (CPR) treatment to a person in need of emergencyassistance includes obtaining, by a computing unit, from anaccelerometer positioned to move in coordination with a patient'sbreastbone values for depths of a plurality of the chest compressions.The method also includes obtaining, by a computing unit, from a lightsensor affixed to the patient information about light detection. Themethod also includes determining, based on the information from thelight sensor, whether a rescuer is releasing the chest of a patientduring manual CPR chest compressions. The method also includes providingfeedback to a rescuer about chest compressions performed by the rescuerbased at least in part on the values for the depths of the plurality ofthe chest compressions and the determination of whether the rescuer isreleasing the chest of the patient.

Embodiments can include one or more of the following.

Determining whether the rescuer is releasing the chest of a patientduring manual CPR chest compressions can include determining a frequencyat which light is detected by the light sensor, comparing the determinedfrequency with a compression rate obtained from the accelerometer, anddetermining that the rescuer is not releasing the chest of a patient ifthe determined frequency at which light is detected by the light sensoris less than the compression rate obtained from the accelerometer.

Providing the feedback to the rescuer about chest compressions caninclude displaying on a graphical display screen of a defibrillator, anindication of the depths of one or more of the plurality of the chestcompressions, the rate of the chest compressions, and a releaseindicator.

Providing the feedback to the rescuer about chest compressions caninclude displaying a release indicator where the amount of fill in therelease indicator varies to indicate whether the rescuer is fullyreleasing between chest compressions.

Providing the feedback to a rescuer about chest compressions can includedisplaying an icon that indicates whether the chest compressions arebeing performed properly.

The method can also include receiving information about the patient'sheart activity and displaying on a graphical display, with the feedbackabout chest compressions, an electrocardiogram of the patient.

The computing unit can be integrated with a portable defibrillator.

The computing unit can be a touchscreen tablet computer.

In some aspects, an external defibrillator includes a light sensorarranged to contact a patient and obtain measurements regarding lightdetection, a computing unit connected to memory that stores computerinstructions for determining, based on the information from the lightsensor, whether a rescuer is releasing the chest of a patient duringmanual CPR chest compressions, and a video display screen for displayingfeedback to a rescuer about chest compressions performed by the rescuerbased at least in part on the determination of whether the rescuer isreleasing the chest of the patient.

Embodiments can include one or more of the following.

The computing unit can be configured to determine whether the rescuer isreleasing the chest of a patient during manual CPR chest compressions bydetermining a frequency at which a threshold amount of light is detectedby the light sensor, comparing the determined frequency with acompression rate obtained from an accelerometer, and determining thatthe rescuer is not releasing the chest of a patient if the determinedfrequency at which a threshold amount of light is detected by the lightsensor is less than the compression rate obtained from theaccelerometer.

The feedback to the rescuer about chest compressions can include arelease indicator.

An amount of fill in the release indicator can vary to indicate whetherthe rescuer is fully releasing between chest compressions.

The feedback to the rescuer about chest compressions can include an iconthat indicates whether the chest compressions are being performedproperly.

The external defibrillator can also include one or more sensorsconfigured to obtain information about the patient's heart activity.

The video display can be further configured to display anelectrocardiogram of the patient with the feedback about chestcompressions.

In some additional aspects, a method for providing adaptiveCardiopulmonary Resuscitation (CPR) treatment to a person in need ofemergency assistance includes obtaining, by a computing unit, from anaccelerometer positioned to move in coordination with a patient'sbreastbone values for depths of a plurality of the chest compressions,obtaining, by a computing unit, from a capacitive touch sensor affixedto the patient information about contact with the sensor, determining,based on the information from the capacitive touch sensor, whether arescuer is releasing the chest of a patient during manual CPR chestcompressions, and providing feedback to a rescuer about chestcompressions performed by the rescuer based at least in part on thevalues for the depths of the plurality of the chest compressions and thedetermination of whether the rescuer is releasing the chest of thepatient.

Embodiments can include one or more of the following.

Determining whether the rescuer is releasing the chest of a patientduring manual CPR chest compressions can include determining a frequencyat which contact with the capacitive touch sensor is detected based onthe information from the capacitive touch sensor, comparing thedetermined frequency with a compression rate obtained from theaccelerometer, and determining that the rescuer is not releasing thechest of a patient if the determined frequency at contact is detected bythe capacitive touch sensor is less than the compression rate obtainedfrom the accelerometer.

Providing the feedback to the rescuer about chest compressions caninclude displaying on a graphical display screen of a defibrillator, anindication of the depths of one or more of the plurality of the chestcompressions, the rate of the chest compressions, and a releaseindicator.

Providing the feedback to the rescuer about chest compressions caninclude displaying a release indicator where the amount of fill in therelease indicator varies to indicate whether the rescuer is fullyreleasing between chest compressions.

Providing the feedback to a rescuer about chest compressions can includedisplaying an icon that indicates whether the chest compressions arebeing performed properly.

The method can also include receiving information about the patient'sheart activity and displaying on a graphical display, with the feedbackabout chest compressions, an electrocardiogram of the patient.

In some additional aspects, an external defibrillator includes acapacitive touch sensor arranged to contact a patient and obtainmeasurements regarding contact with the capacitive touch sensor, acomputing unit connected to memory that stores computer instructions fordetermining, based on the information from the capacitive touch sensor,whether a rescuer is releasing the chest of a patient during manual CPRchest compressions, and a video display screen for displaying feedbackto a rescuer about chest compressions performed by the rescuer based atleast in part on the determination of whether the rescuer is releasingthe chest of the patient.

Embodiments can include one or more of the following.

The computing unit can be configured to determine whether the rescuer isreleasing the chest of a patient during manual CPR chest compressions bydetermining a frequency at which a capacitance indicative of contact ofa rescuer's hands with the capacitive touch sensor is detected by thecapacitive touch sensor, comparing the determined frequency with acompression rate obtained from an accelerometer, and determining thatthe rescuer is not releasing the chest of a patient if the determinedfrequency at which a threshold amount of light is detected by the lightsensor is less than the compression rate obtained from theaccelerometer.

The feedback to the rescuer about chest compressions can include arelease indicator with an amount of fill in the release indicatorvarying to indicate whether the rescuer is fully releasing between chestcompressions.

The feedback to the rescuer about chest compressions can include an iconthat indicates whether the chest compressions are being performedproperly.

The defibrillator can be further configured to receive information aboutthe patient's heart activity and displaying on a graphical display, withthe feedback about chest compressions, an electrocardiogram of thepatient.

In some additional aspects, a system for assisting a rescuer inperforming cardio-pulmonary resuscitation (CPR) on a patient isprovided. The system comprises: a proximity sensor configured to bepositioned at a location corresponding to a location of a rescuer's handwhen delivering compressions to a patient's chest, the proximity sensorconfigured to produce a signal indicative of the rescuer's hands beingreleased from the patient's chest; a medical device operatively coupledwith the proximity sensor and configured to provide resuscitativetreatment to the patient; and a controller communicatively coupled withthe medical device and the proximity sensor. The controller isconfigured to: determine, based upon the signal from the proximitysensor, if the rescuer's hands have been released from the patient'schest, and trigger an action by the medical device in response to adetermination that the rescuer's hands have been released from thepatient's chest.

The proximity sensor can comprise at least one of a capacitive sensor,an ultrasonic sensor, an E-field sensor, and a light emitter-receiverpair. The determination that the rescuer's hands have been released fromthe patient's chest can be based on a measurement from the proximitysensor that the rescuer's hands are greater than 1 cm away from thepatient's chest.

The medical device can be a defibrillator comprising an electricalstorage device capable of delivering a therapeutic pulse to a patient.The action can be charging the electrical storage device of thedefibrillator.

At least one sensor can be operatively connected to the controller forobtaining one or more electrocardiogram (ECG) signals from the patient.The controller can be further configured to: determine, based upon thesignal from the proximity sensor, if the rescuer's hands are in contactwith the patient's chest, analyze the one or more ECG signals from thepatient during delivery of chest compressions to the patient, anddetermine a desirability of a shock to the patient based on the analysisof the one or more ECG signals during the delivery of chest compressionsof a CPR cycle. The action can be an analysis of one or more ECG signalsacquired in an absence of chest compressions to reconfirm thedesirability of the shock to the patient, the absence of chestcompressions being based on the determination of whether the rescuer'shands have been released from the patient's chest. In some examples, thecontroller can be configured to: perform at least one transformation ofat least a portion of the one or more ECG signals from the patient intofrequency domain data based on the determination of whether therescuer's hands have been released from the patient's chest, determine afirst frequency-based value over a first evaluation period based on theat least one transformation, determine a second frequency-based valuerepresenting a trend over a second evaluation period based on the atleast one transformation, determine a probability of therapeutic successbased at least in part on the first frequency-based value and the secondfrequency-based value, and provide an indication of the probability oftherapeutic success. The first frequency-based value can comprise anamplitude spectral area (AMSA) value and the second frequency-basedvalue comprises an AMSA trend.

The medical device can comprise a feedback device operatively connectedto the controller. The feedback device can be configured to providefeedback received from the controller to the rescuer regardingcompressions. The action can be providing an indication via the feedbackdevice to provide ventilation to the patient. The indication can be atleast one of an audio indication and a visual indication.

In some additional aspects, a method for assisting a rescuer inperforming cardio-pulmonary resuscitation (CPR) on a patient comprises:positioning a proximity sensor at a location corresponding to a locationof a rescuer's hand when delivering compressions to a patient's chest;producing, with the proximity sensor, a signal indicative of therescuer's hands being released from the patient's chest; determining,based upon the signal from the proximity sensor, if the rescuer's handshave been released from the patient's chest; and triggering an action bya medical device in response to a determination that the rescuer's handshave been released from the patient's chest.

The method may also comprise obtaining one or more electrocardiogram(ECG) signals from the patient. The method may also further comprise:determining, based upon the signal from the proximity sensor, if therescuer's hands are in contact with the patient's chest, analyzing theone or more ECG signals from the patient during delivery of chestcompressions to the patient; and determining a desirability of a shockto the patient based on the analysis of the one or more ECG signalsduring the delivery of chest compressions of a CPR cycle. The action canbe an analysis of one or more ECG signals acquired in an absence ofchest compressions to reconfirm the desirability of the shock to thepatient, the absence of chest compressions being based on thedetermination of whether the rescuer's hands have been released from thepatient's chest.

Alternatively, the action can be: performing at least one transformationof at least a portion of the one or more ECG signals from the patientinto frequency domain data based on the determination of whether therescuer's hands have been released from the patient's chest; determininga first frequency-based value over a first evaluation period based onthe at least one transformation; determining a second frequency-basedvalue representing a trend over a second evaluation period based on theat least one transformation; determining a probability of therapeuticsuccess based at least in part on the first frequency-based value andthe second frequency-based value; and providing an indication of theprobability of therapeutic success. The first frequency-based value maycomprise an amplitude spectral area (AMSA) value and the secondfrequency-based value comprises an AMSA trend.

The action can also be providing an indication to ventilate the patient.

Other features and advantages will be apparent from the description anddrawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWING(S)

FIG. 1A is a diagram of one implementation including an automaticelectronic defibrillator (AED) and a multiple lead electrocardiograph(ECG) device.

FIG. 1B is a diagram of the AED of FIG. 1A.

FIG. 2 is a diagram of a defibrillation device with a display.

FIG. 3 is a flow chart showing actions taken to provide a releaseindicator.

FIGS. 4A and 4B are screenshots showing exemplary information presentedon a defibrillator display.

FIG. 5 is a diagram of defibrillation electrodes attached to a victim.

FIGS. 6A and 6B are diagrams of a victim receiving CPR.

FIGS. 7A and 7B are diagrams showing the placement of the hands relativeto a light sensor during the administration of CPR to a victim.

FIG. 8A shows an electrode package.

FIGS. 8B and 8C show defibrillation electrodes prior to removal from abacking.

FIGS. 9A and 9B are diagrams of a victim receiving CPR.

FIGS. 10A and 10B are diagrams showing the placement of the handsrelative to a capacitive sensor during the administration of CPR to avictim.

FIGS. 11A and 11B show anterior and posterior electrode assemblies,respectively, applied to a patient.

FIG. 12 is a block diagram of an exemplary system.

FIG. 13 shows a schematic for an E-field proximity sensor.

FIG. 14 is a flow chart of a method for detecting and using a rescuer'sproximity to determine when to deliver a defibrillation shock.

FIG. 15 shows an example schematic for identifying a presence of ashockable rhythm in ECG data.

FIG. 16 shows a flowchart of an example processes for identifying apresence of a shockable rhythm in ECG data.

FIGS. 17A-17F show examples of ECG waveforms in relation to CPRtreatments.

FIG. 18 is an example display including ECG, AMSA, and CPRrepresentations.

DESCRIPTION OF THE INVENTION

This description discusses systems and techniques for using a proximitysensor to assist in resuscitation efforts of a patient. A proximitysensor may be used to detect whether the hands of a rescuer or acompression device is in contact with a patient. Depending on whetherthere is contact, various actions that are helpful to enhanceresuscitation of the patient may be triggered.

In certain embodiments, the proximity sensor may generate informationfor providing feedback to a user/rescuer about the quality of CPR chestcompressions. For example, detection of whether the hands are in contactwith the patient may useful to determine whether the rescuer isappropriately releasing the chest of the victim during chestcompressions, or whether the rescuer has initiated contact with thepatient to begin a chest compression.

When it is determined that the rescuer has paused chest compressions fora brief interval of time (e.g., 1-3 seconds, 1-5 seconds, 1-10 seconds),then other activities may be performed. For example, during the pause,it may be beneficial to perform certain types of analyses on the ECG ofthe patient (e.g., ECG shock analysis, frequency transform analysis,amplitude spectrum area analysis). That is, artifacts that arise in theECG due to the administration of chest compressions may be avoided byconfirming or otherwise detecting that a chest compression is notoccurring and performing the calculation or analysis during the pause inchest compression. Also, during pauses in chest compressions, it may bepreferable to administer one or more positive pressure breathventilations to the patient. Such a pause in chest compressions may besufficiently long for a ventilation to be safely administered to thepatient. Otherwise, the pressure generated within the thorax due to achest compression may be injurious to the patient if a positive pressureventilation is administered concurrently with chest compressions.

Referring now to FIG. 1A, an AED 10 is shown that may be used to providea defibrillation shock at an appropriate time. In the figure, whichshows an example implementation, a rescuer uses an AED 10 toautomatically monitor a victim during cardiac resuscitation. The AED 10uses measured ECG signals to monitor the victim's heart, and charges thedefibrillation device within the AED while the victim is resuscitatedusing chest compressions techniques. In some examples, the manner inwhich the defibrillation device is charged (e.g., the rate of charge,the total amount of charge stored) can be based on the measured ECGsignals. Advantageously, charging the defibrillation device during CPRchest compressions reduces the amount of time that the victim is notreceiving chest compressions because, if a shockable rhythm exists, thedevice is armed and ready to deliver the shock as soon as the rescuercompletes the chest compressions.

As shown in FIG. 1B, the AED 10 includes a speaker 16, a display screen18, an analog-to-digital converter 20, a processor 22, and adefibrillator pulse generator 24. The analog-to-digital converter 20 isconnected to a set of ECG leads that are in turn attached to the victim.The ECG leads pass signals to the processor 22 for monitoring theelectrical rhythms of the victim's heart. The converter 20 sends thesignals from the ECG leads to the processor 22. The processor 22monitors the victim's heart for dangerous rhythms using the ECG signalswhile the victim is resuscitated using chest compressions techniques.

If the AED 10 detects a dangerous heart rhythm, the AED 10 generates analert signal. The alert signal is noticeable to the rescuer. The AED 10can generate a defibrillating shock to the victim when the rescuerissues a command to the AED 10 directing such a shock. Thedefibrillating shock is intended to remedy the dangerous rhythm of thevictim's heart.

The AED 10 also includes a charging module that may be configured tocharge the AED during chest compressions. The module can adaptivelycharge the AED based on monitored ECG signals and patient age. In someexamples, the defibrillator is pre-charged only if a shockable rhythm islikely to exist as determined by analysis of the monitored ECG signals.In some additional examples, the level of charge for the device isdetermined and set based on the monitored ECG signals. In someadditional examples, the method of charging (e.g., the rate of charge)varies based on the monitored ECG signals in an effort to conservepower. For example, if time allows, a capacitor may be charged moreslowly than it normally would in order to conserve power, but stillensure that the capacitor will reach its full charge just as thedefibrillator is needed by the rescuer.

The AED 10 uses a rhythm advisory method for, a) quantifying thefrequency-domain features of the ECG signals; b) differentiating normaland abnormal ECG rhythms, such as VF; c) detecting the onset of abnormalECG rhythms; and d) making decisions about the physiological states ofthe heart. This frequency-domain measure can be reliable with or withoutthe presence of the chest compression artifact in the ECG signals. TheAED 10, after identifying the current physiological state of the heart,can make a decision about appropriate therapeutic action for the rescuerto make and communicate the action to the rescuer using the speaker 16and the display screen 18.

The AED 10 may incorporate functionality for performing additionaltherapeutic actions such as chest compressions, ventilations, ordelivery of intravenous solution-containing metabolic or constitutivenutrients. Based on the results of the analysis of the rhythm advisorymethod, the AED 10 may automatically deliver the appropriate therapy tothe patient.

The AED 10 may also be configured in “advisory” mode wherein the AED 10will prompt the caregiver after the AED 10 has made a determination ofthe best therapy, and acknowledgement by the caregiver/device operator,in the form of a button press or voice-detected acknowledgement, isrequired before therapy is delivered to the patient.

The AED 10 analyzes the ECG signals to predict defibrillation success aswell as to decide whether it is appropriate to defibrillate or todeliver an alternative therapy such as chest compressions, drugs such asepinephrine, constitutive nutrients such as glucose, or other electricaltherapy such as pacing.

In some examples, one or more therapeutic delivery devices 30automatically deliver the appropriate therapy to the patient. Thetherapeutic delivery devices 30 can be, for example, a portable chestcompression device, a drug infusion device, a ventilator and/or a devicethat includes multiple therapies such as defibrillation, chestcompression, ventilation and drug infusion. The therapeutic deliverydevices 30 are physically separate from the defibrillator AED 10, andcontrol of the therapeutic delivery devices 30 may be accomplished by acommunications link 32. The communications link 32 may take the form ofa cable but preferably the link 32 is via a wireless protocol.

In other examples, control and coordination for the overallresuscitation event and the delivery of the various therapies may beaccomplished by a device 34 or processing element that is external tothe AED 10. For instance, the device 34 may download and process the ECGdata from the AED 10; analyze the ECG signals, perform relevantdeterminations like those discussed above and below based on theanalysis, and control the other therapeutic devices 30, including theAED 10. In other examples, the AED 10 may perform all the processing ofthe ECG, including analyzing the ECG signals, and may transmit to thecontrol device 34 only the final determination of the appropriatetherapy, whereupon the control device 34 would perform the controlactions on the other linked devices 30.

Chest compression artifacts can be separated from the ECG signalcomponents, making it possible for the AED 10 to process the ECG signalwithout halting the processing during chest compressions. Exemplarymethods for analyzing the ECG signal to determine if a shockable rhythmexists are described, for example, in U.S. Pat. No. 7,565,194, titled“ECG Rhythm Advisory Method,” the contents of which are herebyincorporated by reference in their entirety.

It has been recognized that good chest compressions during CPR isessential to saving more victims of cardiac arrest. The compression raterecommended by the American Heart Association in its guidelines is equalor greater than 100 compressions per minute. Many studies have reportedthat the discontinuation of chest compressions, such as is commonly donefor ECG analysis and charging of a defibrillator, can significantlyreduce the recovery rate of spontaneous circulation and 24-hour survivalrate. Because of safety issues with delivery of a high voltagedefibrillation shocks with voltages of 1000-2000 volts, rescuers aretaught to cease chest compressions and remove their hands from thevictim's chest before initiating the defibrillation shock. By analyzingECG signals during chest compressions as a mechanism to permit earliercharging of an energy delivery device (e.g., a capacitor) in adefibrillator device, the gaps in providing chest compressions can bereduced, and patient care increased.

FIG. 2 shows a defibrillation device with a display portion thatprovides information about patient status and CPR administration qualityduring the use of the defibrillator device. The data is collected anddisplayed in an efficient and effective manner to a rescuer. As shown onthe display, during the administration of chest compressions, the devicedisplays information about the chest compressions in box 54 on the samedisplay as a filtered ECG waveform 50 and a CO2 waveform 52(alternatively a SpO2 waveform can be displayed).

During chest compressions, the ECG waveform is generated by gatheringECG data point and accelerometer readings and filtering the motioninduced (e.g., CPR induced) noise from the ECG waveform. Measurement ofvelocity or acceleration of chest compression during chest compressionscan be performed according to the techniques taught by U.S. Pat. No.7,220,335, Method and Apparatus for Enhancement of Chest CompressionsDuring Chest Compressions, the contents of which are hereby incorporatedby reference in their entirety. Displaying the filtered ECG waveformhelps clinicians reduce interruptions in CPR because the displayedwaveform is easier for the rescuer to decipher. If the ECG waveform isnot filtered, artifacts from manual chest compressions make it difficultto discern the presence of an organized heart rhythm unless compressionsare halted. Filtering out this artifact allows clinicians to view theunderlying rhythm without stopping chest compressions.

As shown in the display, the filtered ECG waveform 50 is a full lengthwaveform filling the entire span of the display device while the secondwaveform (e.g., the CO2 waveform 52) is a partial length waveform andfills only a portion of the display. A portion of the display beside thesecond waveform provides the CPR information in box 54. For example, thedisplay splits the horizontal area for the second waveform in half,displaying waveform 52 on left and CPR information on the right in box54.

The CPR information in box 54 is automatically displayed whencompressions are detected. The information about the chest compressionsdisplayed in box 54 includes rate 58 (e.g., number of compressions perminute) and depth 56 (e.g., depth of compressions in inches ormillimeters). The rate and depth of compressions can be determined byanalyzing accelerometer readings. Displaying the actual rate and depthdata (in addition to or instead of an indication of whether the valuesare within or outside of an acceptable range) is believed to provideuseful feedback to the rescuer. For example, if an acceptable range forchest compression depth is between 1.5-2 inches, providing the rescuerwith an indication that his/her compressions are only 0.5 inches canallow the rescuer to determine how to correctly modify his/heradministration of the chest compressions.

The information about the chest compressions displayed in box 54 alsoincludes a perfusion performance indicator (PPI) 60. The PPI 60 is ashape (e.g., a diamond) with the amount of fill in the shape differingto provide feedback about both the rate and depth of the compressions.When CPR is being performed adequately, for example, at a rate of about100 compressions/minute (CPM), with the depth of each compressiongreater than 1.5 inches, the entire indicator will be filled. As therate and/or depth decreases below acceptable limits, the amount of filllessens. The PPI 60 provides a visual indication of the quality of theCPR such that the rescuer can aim to keep the PPI 60 completely filled.While some exemplary types of information displayed to the rescuer havebeen described herein, additional information about CPR quality andphysiological parameters of the victim can be displayed in conjunctionwith or instead of the information described herein. For example, arelease indication can be displayed with other information about the CPRquality of measured physiological parameters. Exemplary displays andmeasurements are described, for example, in Ser. No. 13/025,348 filed onFeb. 11, 2011, now U.S. Pat. No. 8,880,166, issued on Nov. 4, 2014 andentitled “DEFIBRILLATOR DISPLAY” and in Ser. No. 13/081,217 filed onApr. 6, 2011, now U.S. Pat. No. 9,364,625, issued on Jun. 14, 2016 andentitled “WIRELESS VENTILATOR REPORTING,” the contents of each of whichare hereby incorporated by reference.

In addition to measuring information about the rate and depth of CPRchest compressions, in some examples the defibrillator device providesinformation about whether the rescuer is fully releasing his/her handsat the end of a chest compression. For example, as a rescuer tires, therescuer may begin leaning on the victim between chest compressions suchthat the chest cavity is not able to fully expand at the end of acompression. If the rescuer does not fully release between chestcompressions the quality of the CPR can diminish. As such, providing avisual or audio indication to the user when the user does not fullyrelease can be beneficial.

FIG. 3 is a flow chart showing actions taken to provide an indication ofwhether a rescuer is fully releasing between chest compressions. At box62, the defibrillator device measures depth, rate, and release of CPRchest compressions. The depth, rate, and release of CPR chestcompressions can be determined based on information collected from anaccelerometer, light sensor, capacitive touch sensor, or other devices.Based on the collected information, at box 64, the defibrillatordetermines whether the rescuer is fully releasing between chestcompressions. At box 66, the defibrillator provides an indicator on adisplay that includes information about whether the rescuer is fullyreleasing. For example, the display on the defibrillator can include arelease indication box where the amount of fill in the box varies toindicate whether the rescuer is fully releasing between chestcompressions. For example, as shown in FIG. 4A, when the rescuer isfully releasing the box 70 can be fully filled. When the rescuer is notfully releasing the amount of fill in the release indication box isdecreased such that the box is only partially filled (e.g., as shown inbox 72 of FIG. 4B).

In some examples, the depth and rate of CPR chest compressions can bedetermined based on information collected from an accelerometer whilethe release of the CPR chest compressions can be based on informationcollected from a light or capacitive touch sensor, or some other type ofproximity sensor. For example, as shown in FIG. 5, a CPR monitoringdevice 86 that includes a light sensor or capacitive touch sensor 88 andan accelerometer can be affixed to a victim's chest at a locationcorresponding to the location of the rescuer's hands when deliveringmanual chest compressions prior to the administration of CPR. The lightsensor measures light impinging on the sensor and provides theinformation to a computing device in the defibrillator. Thedefibrillator processes the information to determine whether therescuer's hands are in contact with the light sensor 88. Moreparticularly, because the device 86 is affixed to the victim's chest oron top of the CPR sensor at a location corresponding to the location ofthe rescuer's hands when delivering manual chest compressions, thepresence or absence of light detection by the light sensor 88 can beused to determine whether the rescuer is making contact with thepatient's body. That is, based on information detected from thesensor(s) (e.g., proximity sensor, accelerometer, E-field sensor, lightsensor, etc.), it can be determined whether the rescuer is initiating achest compression or whether the rescuer is fully releasing the chest ofthe victim during the administration of chest compressions.

Practically speaking, depending on the type of proximity sensoremployed, the proximity sensor measures a signal indicative of arelevant physical property (e.g., E-field, capacitance, light reflectedfrom the rescuer's hands, ambient light, etc.) and then the relativeproximity of the hands to the patient is estimated. For example, for alight sensor, if a substantial amount of light is sensed, then the handsmay be estimated to be relatively far away from the patient; converselyif a small amount or no light is sensed, then the hands may be estimatedto be close to, or perhaps in contact with, the patient. An appropriatethreshold or suitable criterion may be employed to determine whether thevalues produced by the proximity sensor would qualify as the hands beingin contact with the patient or not in contact with the patient.

The light sensor 88 can be any device that is used to detect light.Exemplary light sensors include photocells or photoresistors that changeresistance when light shines on it, charged coupled devices (CCD) thattransport electrically charged signals, photomultipliers that detectlight and multiply it, and the like. Capacitive sensing is a technologybased on capacitive coupling between conductive or has a dielectricdifferent than that of air and the sensor. When the human handsapproaches or touches the capacitive sensor, this detects this movementor touch of the hand and measure a change in capacitance. The level ofcapacitance can be used by the processor or device to determine whetherthe rescuer hand is touching the capacitor sensor pad. For example, theprocessor or device may analyze the level of capacitance recorded by thecapacitive sensor and determine whether the level of capacitance fallswithin a set criterion for whether the hands are in contact with thepatient or not in contact with the patient.

As discussed herein, any suitable proximity sensor may be employed. Theoutput of the proximity sensor is calibrated according to methods knownby those of skill in the art to estimate a distance of the rescuer'shands from the patient. For instance, a greater amount of light sensedby a light sensor may indicate that the rescuer's hands are further awayfrom the patient. Similarly, the recorded capacitance, voltage, E-field,or other value, may be indicative of the distance of the rescuer's handsfrom the patient. In various embodiments, if the estimated distance ofthe rescuer's hands from the patient is greater than a certain distance(e.g., greater than 1 mm, greater than 5 mm, greater than 1 cm, greaterthan 2 cm, greater than 3 cm, greater than 4 cm, greater than 5 cm,greater than 6 cm, greater than 7 cm, greater than 8 cm, greater than 9cm, greater 10 cm, etc.), then it may be determined that the rescuer'shands are not in contact with the patient, or released from (following acompression) the patient.

FIGS. 6A-B and 7A-B show exemplary light sensor during CPR compressions.As shown in FIGS. 6A and 7A, when the rescuer's hands 92 are raised awayfrom the victim's chest and are not in contact with the victim's chest90 (e.g., when the rescuer releases from a compression), the lightsensor 88 is uncovered. Thus, when the rescuer's hands are raised awayfrom the victim's chest light 96 can reach the light sensor 88 and thelight sensor detects the presence of the light 96. In contrast, as shownin FIGS. 6B and 7B, when the rescuer's hands 92 are in contact with thevictim's chest 90 (e.g., when the rescuer is providing a compression)the light sensor 88 is covered. When the light sensor is covered, lightis not able to reach the light sensor 88. Thus, the presence and absenceof light measured by the light sensor can be used to determine whetherthe rescuer is fully releasing his/her hands from the victim's chest 90;when light is detected the rescuer has released and when light is notdetected the rescuer is maintaining physical contact with the victim.Similarly, when the rescuer's hands are off the chest, it can then bedetermined whether the rescuer has made contact with the patient so asto initiate a subsequent chest compression. When the rescuer hasinitiated contact, information from the accelerometer can then be usedto determine the chest compression depth.

In some examples, the information from the light sensor can be comparedto CPR compression rate information from the accelerometer to determinewhether the user is releasing the victim's chest fully. Moreparticularly, if the rescuer is releasing the victim's chest fully,light should be observed by the light sensor for every compression.Thus, the defibrillation device can determine a frequency at which athreshold amount of light is detected by the light sensor and comparethe determined frequency with a compression rate obtained from theaccelerometer. If the determined frequency from the light sensor is thesame (or within an acceptable range from) the compression rate obtainedfrom the accelerometer, the defibrillation device can determine that therescuer is appropriately releasing the victim's chest. On the otherhand, if the frequency from the light sensor is less than thecompression rate, the defibrillation device can determine that therescuer is not appropriately releasing the victim's chest.

While in the example described above, the presence/absence of light wasused to determine the release of the rescuer's hands from the victim'schest, in some additional examples a change in light measured by thelight sensor 88 can be used to determine the presence/absence of therescuer's hands. For example, the rescuer may not fully cover the lightsensor 88 when providing compressions. However, if a portion of thelight sensor 88 is covered, a change in the intensity or amount of lightmeasured by the light sensor will be observed when the rescuer liftshis/her hands. This change in intensity can be used to determinepresence/absence of the rescuer's hands.

In some additional examples, the light sensor 88 can be used to detectthe removal of the electrodes from a package and can be used to begininstructions to a rescuer about how to apply the electrodes to thevictim.

FIG. 8A shows an assembled electrode package 100 with multiconductorelectrical lead 120 and label 112. The package is opened by grasping theloose flaps 116 at arrow label 118, and peeling back the top flap. Asthe flaps are pulled apart, releaseable peripheral adhesive 114 parts.When a light sensor is included in the assembled electrode package 110,light is unable to impinge on the light sensor 161. As such, informationfrom the sensor can be used to determine that the rescuer has not yetopened the electrode package regardless of whether the leads 120 havebeen plugged into a defibrillation device. As such, if thedefibrillation device detects that the leads 120 have been inserted intothe defibrillation device but the light sensor 161 does not indicate thepresence of light, the defibrillation device can provide instructions tothe rescuer about how to open the electrode package 100.

FIGS. 8B and 8C show views of the electrodes 150 a and 150 b, anaccelerometer 160, a light sensor 161, and styrene sheet 140 afterremoval from the electrode package 100. Before the package is opened,the styrene sheet 140 is folded along fold line 151 in the form of aclosed book (e.g., as shown in FIG. 8B), with the electrodes 150 a and150 b and accelerometer 160 peelably attached to the interior facingsurfaces of the book. The accelerometer works with electronics in thedefibrillator to determine the depth of compressions during CPR. Thelight sensor 161 works with electronics in the defibrillator todetermine whether the rescuer is appropriately releasing the victim'schest between compressions (e.g., as described herein). ECG electrodes(not shown) are built into one of electrode 150 a or 150 b (each islocated at approximately the corners of the triangular shape of theelectrode). Until the book is unfolded, the light sensor 161 is coveredby the opposite side of the styrene sheet 140 and light is unable toimpinge on the light sensor. On opening the package, the book isunfolded, so that the electrodes and accelerometer are presented to theuser as shown in FIG. 8C. Upon unfolding the book, the light sensor 161is uncovered and light is able to reach the light sensor. Thus, theunfolding of the book (and the resulting light measurement from thesensor 161) indicates to the defibrillation device that the user hasopened the package 100 and is ready to receive information (e.g., audioor visual instructions) about the application of the electrodes to thevictim.

FIGS. 9A-B and 10A-B show a capacitive sensor during CPR compressions.As shown in FIGS. 9A and 10A, when the rescuer's hands 92 are raisedaway from the victim's chest and are not in contact with the victim'schest 90 (e.g., when the rescuer releases from a compression), thecapacitive sensor 87 is uncovered. Thus, when the rescuer's hands areraised away from the victim's chest capacitive measured by thecapacitive sensor 87 is based on the dielectric of air. In contrast, asshown in FIGS. 9B and 10B, when the rescuer's hands 92 are in contactwith the victim's chest 90 (e.g., when the rescuer is providing acompression) the capacitive sensor 87 is covered and contact is madebetween the rescuer's hands and the sensor 87. When the human handsapproach or touch the capacitive sensor 87, the sensor 87 detects thismovement or touch of the hand and measures a change in capacitance.Thus, the measured capacitance level can be used by the processor ordevice to determine whether the rescuer hand is touching the capacitorsensor 87 and can be used to determine whether the rescuer is fullyreleasing his/her hands from the victim's chest 90; when capacitanceremains at a level indicating that the rescuer's hands are in contactwith the capacitive sensor 87, the rescuer is not fully releasinghis/her hands between compressions.

In some examples, the information from the capacitive sensor can becompared to CPR compression rate information from the accelerometer todetermine whether the user is releasing the victim's chest fully. Moreparticularly, if the rescuer is releasing the victim's chest fully, achange in capacitive should be observed by the capacitive sensor forevery compression. Thus, the defibrillation device or other device usedfor resuscitation can determine a frequency at which a threshold changein capacitance is detected by the capacitive sensor and compare thedetermined frequency with a compression rate obtained from theaccelerometer. If the determined frequency from the capacitive sensor isthe same (or within an acceptable range from) the compression rateobtained from the accelerometer, the defibrillation device can determinethat the rescuer is appropriately releasing the victim's chest. On theother hand, if the frequency from the capacitive sensor is less than thecompression rate, the defibrillation device can determine that therescuer is not appropriately releasing the victim's chest.

While at least some of the embodiments described above describetechniques and displays used in conjunction with an AED device, similartechniques and displays can be used with other defibrillator orresuscitative devices. Exemplary professional grade defibrillatordevices include the R series, E series, Propaq MD, or M series devicesmanufactured by ZOLL Medical, MA and the Philips MRX or Philips XLdevices.

Additionally, the defibrillator may take the form of a wearabledefibrillator such as the LifeVest, manufactured by ZOLL Medical(Chelmsford, Mass.).

Further to the discussion above, good quality compressions with littleor no pausing (e.g., substantially continuous administration ofcompressions) are important for cardiac arrest survival. However, it isdifficult for the average rescuer to provide continuous, high qualitymanual compressions without pauses. In one example, the systems andmethods described herein are configured to automatically detect thecessation or pausing of a rescuer's manual administration of chestcompressions and supplement the treatment of the patient with electricalstimulation during the time periods of such pauses. The electricalstimulation begins automatically based on detected characteristicsrelated to the manual administration of chest compressions such that thetime period between cessation or pausing of the manual chestcompressions and administration of the electrical stimulation is brief(e.g., less than 10 seconds, less than 5 seconds, less than 3 seconds).Examples of such electrical stimulation are described in detail in U.S.patent application Ser. No. 15/175,500, published as US2016/0296418,which is hereby incorporated by reference in its entirety.

In some examples, the electrical stimulation can be administered by, forexample, an anterior electrode assembly (AEA) 190 affixed to thevictim's 202 thorax as described in relation to FIGS. 11A and 11B below.FIGS. 11A and 11B show anterior and posterior electrode assemblies,respectively, applied to a patient.

The AEA 190 is composed of a defibrillation/pacing/monitoring electrode191 known to those skilled in the art, composed of a conductive adhesivegel in contact with the patient's skin, typically also a conductivemetallic surface on the conductive gel for distributing the currentdelivered by the stimulation device, such as a defibrillator 208, and aninsulative top layer. Thus, the AEA 190 can be removably affixed to thepatient's thorax. A housing 194 containing a motion sensor along withpower and signal conditioning electronics is positioned on the patient'ssternum, and is used to measure the motion of the sternum during CPRchest compressions. The motion sensor may be an accelerometer as is usedcommercially in devices of this type (ZOLL CPR Stat-Padz, Chelmsford,Mass.) or may be a pressure sensor, a velocity sensor such as thoseemploying a time-varying magnetic flux and coil arrangement or othervaried motion sensors. Defibrillator 208 processes conditioned motionsensor signal via a Sternal Motion analysis subsystem 226 to determinewhen the rescuer has ceased chest compressions, paused in theadministration of chest compressions, or is no longer administeringeffective chest compressions. The Sternal Motion analysis subsystem 226can be, for example, a software function that is part of the softwarecode for running the Defibrillator 208 in general, or may be specializedhardware either in the defibrillator or in the housing 194 that maycommunicate to the defibrillator microprocessor 230 via, for instance, aserial communication channel such as USB, RS232 or Bluetooth. During thecourse of any typical CPR interval, the duration of which is typicallyon the order of 2 minutes, a rescuer may stop briefly at multiplepoints, sometimes for as little as 3-10 seconds.

FIG. 12 shows an example system 200 for assisting a rescuer inperforming resuscitation activities, in schematic form, and forproviding dynamically controlled chest compression to a patient. Ingeneral, the system 200 involves a number of medical devices that may beused to provide life-saving care to a victim, such as a victim 202, ofsudden cardiac arrest. The various devices may be part of a single unitor multiple units, and may be used to monitor various real-time physicalparameters of the victim 202, to communicate between the components andwith remote systems such as central caregivers, and to provide care tothe victim 202 or provide instructions to caregivers, such as caregiver204, in providing care to the victim 202.

The victim 202 in this example is an individual who has apparentlyundergone sudden cardiac arrest is being treated by the caregiver 204.The caregiver 204 may be, for example, a civilian responder who has hadlimited training in lifesaving techniques, an emergency medicaltechnician (EMT), a physician, or another medical professional. Thecaregiver 204 in this example may be acting alone or may be acting withassistance from one or more other caregivers, such as a partner EMT.

The victim 202 is in a position in which therapy has been provided tothe victim 202. For example, a set of defibrillator electrodes have beenapplied to the victim's torso in a typical manner and are in wiredconnection to a portable external defibrillator 208. The defibrillator208 may be, for example, a typical automated external defibrillator(AED), a professional defibrillator, or other similar type ofdefibrillating apparatus. The victim 202 has also been provided with aventilation bag 206, to provide forced air into the victim's longs toassist in rescue breathing of the victim 202. The defibrillator 208 andventilation bag 206 may be operated in familiar manners and incoordination by various caregivers. Also, the ventilation bag 206 may befitted with various sensors and transmitters so as to communicateelectronically with the defibrillator 208. For example, a volumetricflow sensor may be provided with the ventilation bag 206, and data aboutthe volume of airflow to and from the victim may be passed todefibrillator 208, so the defibrillator 208 may relay such information,or may also use such information to affect the manner in whichdefibrillation is provided to the victim 202.

A computer tablet 214 is also shown communicating with the otherdevices, and being manipulated by caregiver 204. The tablet may serve asa general electronic command post for the caregiver 204 to receiveinformation about the victim 202 and other items, to communicate withother caregivers, and to provide input in controlling the operation ofthe various components in the system 200. The tablet 214 may be providedwith short range and long range wireless communication capabilities,such as Bluetooth or WiFi on the one hand, and cellular 3G or 4G on theother. The caregiver 204 may input information into the tablet computer214, such as information describing the condition of the victim 202 andother similar information that is to be recognized and recorded by thecaregiver 204. The tablet 214 may also be in data communication withmultiple sensors for sensing real-time information about the victim 202,such as blood pressure, pulse, and similar real-time patient parameters.The caregiver 204 may also input information into tablet 214 so as tocontrol one or more of the medical devices being used with the victim202. For example, the user may adjust the type, intensity, speed, orcoordination of treatment that is provided to the victim 202.

Chest compression are delivered manually by the Caregiver 204. In such acase, audiovisual feedback is provided to the Caregiver 204 via Speaker236 a, operatively coupled to audio processing circuitry 236 b, anddisplay 224. Feedback will direct the caregiver 204 to delivercompressions less forcefully when necessary.

As shown in this example, multiple different input signals are receivedthat characterize the current real-time condition or physical parametersof the victim 202. For example, an ECG signal 222 may be received by theMPU 212 and may represent current and real time ECG waveforms for thevictim 202, which may be obtained by leads connected to defibrillator208.

An SpO2 signal 223, or other physiologically-derived signal that iseither a direct or indirect measure of circulatory flow or perfusion, isalso captured at display 224, and may be used to further determine whenand at what force to apply chest compressions to the victim 202.

Note that while FIG. 12 shows specific examples of input signals such asSpO2, an apparatus could use any combination of physiological signalssuch as, but not limited to: ECG; measures of cardiac output; measuresof heart rate; blood pressure(s); oxygen saturation (SpO2); heart sounds(including phonocardiography); heart imaging (including ultrasound);impedance cardiography. Compression parameters could use any combinationof features or measurements of compression including, but not limitedto: compression velocity; compression depth; duty cycle; velocity ofdownstroke and upstroke; intrathoracic pressures during compressions;pleural pressures during compressions; sternal position, velocity oracceleration; chest wall or sternal strain or deformation; force appliedto the chest; pressure used to compress the chest by a mechanical chestcompressor.

A signal processing unit 228 is provided to filter inputs, such as ECGinputs, received from the patient for further analysis by theMicroprocessor 230. For example, the signal processing unit 228 mayfilter noise from input signals, and in the case of ECG data may filterartifacts created by chest compression motion of the victim 202 in orderto remove such artifacts. Such preparation of ECG signals may be termedSEE-THRU CPR, and can be performed as discussed in U.S. Pat. No.6,865,413, filed Jan. 23, 2002, and entitled ECG SIGNAL PROCESSOR ANDMETHOD, the teachings of which are incorporated herein by reference intheir entirety.

The features described can be implemented in digital electroniccircuitry, or in computer hardware, firmware, software, or incombinations of them. The apparatus can be implemented in a computerprogram product tangibly embodied in an information carrier, e.g., in amachine-readable storage device for execution by a programmableprocessor; and method steps can be performed by a programmable processorexecuting a program of instructions to perform functions of thedescribed implementations by operating on input data and generatingoutput. The described features can be implemented advantageously in oneor more computer programs that are executable on a programmable systemincluding at least one programmable processor coupled to receive dataand instructions from, and to transmit data and instructions to, a datastorage system, at least one input device, and at least one outputdevice. A computer program is a set of instructions that can be used,directly or indirectly, in a computer to perform a certain activity orbring about a certain result. A computer program can be written in anyform of programming language, including compiled or interpretedlanguages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, or other unitsuitable for use in a computing environment.

Suitable processors for the execution of a program of instructionsinclude, by way of example, both general and special purposemicroprocessors, and the sole processor or one of multiple processors ofany kind of computer. Generally, a processor will receive instructionsand data from a read-only memory or a random access memory or both. Theessential elements of a computer are a processor for executinginstructions and one or more memories for storing instructions and data.Generally, a computer will also include, or be operatively coupled tocommunicate with, one or more mass storage devices for storing datafiles; such devices include magnetic disks, such as internal hard disksand removable disks; magneto-optical disks; and optical disks. Storagedevices suitable for tangibly embodying computer program instructionsand data include all forms of non-volatile memory, including by way ofexample semiconductor memory devices, such as EPROM, EEPROM, and flashmemory devices; magnetic disks such as internal hard disks and removabledisks; magneto-optical disks; and CD-ROM and DVD-ROM disks. Theprocessor and the memory can be supplemented by, or incorporated in,ASICs (application-specific integrated circuits).

To provide for interaction with a user, the features can be implementedon a computer having a display device such as a CRT (cathode ray tube)or LCD (liquid crystal display) monitor for displaying information tothe user and a keyboard and a pointing device such as a mouse or atrackball by which the user can provide input to the computer.

The features can be implemented in a computer system that includes aback-end component, such as a data server, or that includes a middlewarecomponent, such as an application server or an Internet server, or thatincludes a front-end component, such as a client computer having agraphical user interface or an Internet browser, or any combination ofthem. The components of the system can be connected by any form ormedium of digital data communication such as a communication network.Examples of communication networks include a local area network (“LAN”),a wide area network (“WAN”), peer-to-peer networks (having ad-hoc orstatic members), grid computing infrastructures, and the Internet.

The computer system can include clients and servers. A client and serverare generally remote from each other and typically interact through anetwork, such as the described one. The relationship of client andserver arises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other.

The computer system may include software for implementing an electronicpatient care record, for example the ePCR software of ZOLL Data Systems(Broomfield Colo.). The software provides the ability to enter, storeand transmit patient information as well as therapeutic interactions.The computer is often a so-called “Tablet” computer system that has beenruggedized for pre-hospital use, but may also take the form of an iPhoneor iPad. Data is preferably transmitted in real time between theportable “Tablet” computer 214 to the MPU 212.

In some embodiments, the sensor housing 194 and electrodes areconfigured to ensure that the rescuer's hands have been removed from thepatient (e.g., are not in contact with the patient) prior toadministration of a defibrillation shock and or delivery the electricalstimulations for generating perfusion. For example, the sensor housingcan include a proximity sensor (e.g., a capacitive sensor) thatdetermines whether a rescuer is in contact with the patient andprohibits delivery of electrical current to the patient when the rescueris in contact with the patient. In some additional examples, asdescribed in more detail below, the system can be configured tocoordinate the delivery of the defibrillation shock with the detectionthat the rescuer has removed his/her hands from the patient. Forexample, the defibrillation shock can be delivered automatically andwithout requiring further user action upon detection that the rescuerhas removed his/her hands from the patient.

The sensor housing 194 may also contain the proximity sensor 216 formeasuring the location of the rescuer's hands. This measurement ofrescuer hand location may be used in several possible ways. In caseswhere the electrode assembly AEA 190 does not incorporate an insulativesheet, the hand location measurement may be used to hold off EPS (e.g.,prohibit delivery of electrical pulses) until the rescuer has removedtheir hands from the patient's chest. Additionally, upon detection offatigue or cessation of manual chest compressions, the device canprovide audio and/or visual prompting to the rescuer instructing them toremove their hands from patient's chest, or to properly release thehands from the patient's chest, until such time as they do remove theirhands. The hand measurement may also be used as a triggering mechanismfor delivery of therapeutic electromagnetic energy (e.g., defibrillationshock) to the patient. It is believed that automatically delivering thetherapeutic electromagnetic energy upon detection of the removal of therescuer's hands can reduce the time between cessation of manual chestcompressions and delivery of the therapeutic electromagnetic energy. Forexample, the defibrillator may be charged during delivery of the manualchest compressions such that the therapeutic electromagnetic energy canbe delivered immediately (e.g., within less than 1 second) after thecessation of manual chest compressions.

Without the automatic detection of the removal of the rescuer's handsand using the detection to trigger the delivery of the therapeuticelectromagnetic energy, when treating a patient who has a shockablerhythm, the defibrillator may be charged by a second rescuer while thefirst delivers ongoing compressions. At the moment for delivering ashock, however, the first rescuer controlling the defibrillator willhave the rescuer delivering stop compressions until after the shock isdelivered by the first rescuer. This involves a set of clearancecommands between the two rescuers, such as saying, “Stand Clear. You'reclear. I'm clear. We're all clear”, then pressing the shock button whenthe first rescuer has made sure that no one is touching the patient.This process can cause for period of no delivery of therapeuticcompressions for 5-10 seconds (e.g., the time lapse between cessation ofchest compressions until the delivery of the electromagnetic energy canbe 5-10 seconds). With the automatic detection of the rescuer proximityto the patient, the first rescuer arms the defibrillator, and then thesecond rescuer who has their hands on the sensor housing 194, deliveringthe compressions, actually causes the defibrillator to deliver thedefibrillation shock by simply lifting their hands from off the sensor.Thus, the electromagnetic energy is automatically delivered upondetection of the removal of the rescuer's hands from the patient. Thisis believed to be particularly effective because the only person whowill be in contact with the patient is the compressor at that point, andthey are in the best position to assess whether anyone else might be incontact. When the rescuer lifts their hands off the sensor housing 194,the proximity sensor 216 detects that the rescuers hands have beenremoved from proximity of the patient and then automatically deliversthe shock.

In some embodiments, E-field sensing such as that provided by theMC33941 (Freescale Semiconductor, document Number: MC33941, Rev 4) canbe used (e.g., as shown in FIG. 10). Because this method of proximitysensing is fundamentally a measure of stray capacitance embodied by therescuer's hands, it is important to calibrate to each rescuer because ofthe variable capacitance interjected by the use of medical gloves, etc.Calibration is accomplished automatically during the time thatcompressions are occurring. Because the sensor housing is beingdepressed during compressions, it can be safely assumed, particularly atthe time when compression is at its deepest point, that the rescuerhands are in direct contact with the surface of the sensor housing 194.The measured capacitance at that point is taken as the zero-distancereference point.

There are additional benefits beyond minimizing the compression pausesduring defibrillation. For instance, it is believed that synchronizingthe defibrillation shock to the early phase of the compression upstrokesignificantly improves shock efficacy. By shocking immediately afterdetection of loss of rescuer hand contact, the defibrillation shock canbe timed to the optimal phase of the compression cycle.

In some additional embodiments, rather than delivering thedefibrillation shock immediately upon detection of removal of therescuer's hands from the patient, one to ten EPS pulses may also bedelivered immediately prior to the defibrillation shock, after theproximity sensor 216 and processor have detected loss of contact withthe rescuer's hands. The defibrillation shock is then synchronized tothe optimal phase of the final EPS pulse.

Alternatives to the E-field proximity sensor 216 are ultrasonic sensorssuch as the MINI_A PB Ultrasonic transducer (SensComp, MI) that has ameasurement range of 1-12 inches. Alternatively, a lightemitter-receiver pair may be located on the rescuer-facing upper surfaceof the sensor housing 194 and be used to detect the instant there is aphysical separation between surface of the sensor housing 194 and therescuer's hands.

FIG. 14 is a flow chart of a method for automatically delivering adefibrillation shock based on the detection of the removal of arescuer's hands from a patient. The system performs a calibration of aproximity sensor by setting a reference point based on a capacitancemeasurement when compressions are being administered 252. The systemanalyzes ongoing capacitance measurements to detect changes incapacitance from reference point 254. Upon detection of significantchange in capacitance (e.g., a change indicative of removal of therescuer's hands from the patient), the system automatically delivers adefibrillation shock to the patient 256.

In many examples it is beneficial to detect when a rescuer has releasedhis/her hands from a patient's chest following chest compressions and/ordetect when a rescuer's hands make contact with a patient's chest toinitiate chest compressions for a variety of reasons. This informationcan be determined using the proximity sensors discussed hereinabove.Once the system determines that the rescuer has released his/her handsfrom the patient's chest following chest compressions and/or detectswhen the rescuer's hands make contact with a patient's chest to initiatechest compressions, the system can also use this information to takevarious actions as discussed hereinafter.

A. Reconfirmation of the Desirability of Delivering a Shock

In certain instances, AED devices utilize a brief period of time (e.g.,while the rescuer locates and presses the button) after the rescuerceases chest compressions to reconfirm the desirability of deliveringthe shock to the victim. For example, a rescuer can be instructed tovisually inspect and confirm that a shockable rhythm exists and/or theAED device can continue to collect and analyze ECG signals (in theabsence of chest compressions resulting in less artifacts in the ECGsignal) to re-confirm the desirability of delivering the shock. Ingeneral, a time period for re-confirmation based on analysis of an ECGsignal without chest compression artifacts can be brief (e.g., less thanabout 5 seconds, less than about 3 seconds, less than about 2 seconds).The time period for re-confirmation can be based on physiologicalcharacteristics (e.g., heart rate that is fast or slow) and/or a desiredconfidence level for the ECG analysis. Such reconfirmation is discussedin United States Patent Application Publication No. 2016/0220833, whichis hereby incorporated by reference in its entirety. Through the use ofa proximity sensor, such as proximity sensor 216, the defibrillator mayautomatically initiate this reconfirmation of whether the patient's ECGis of a shockable or non-shockable nature once the proximity detectordetects that the rescuer's hands have been removed from the patient'schest. Examples of reconfirmation and the use of the proximity detectorare discussed in greater detail below.

In some examples, the caregiver may halt the CPR treatment (e.g., due toexpress instruction to halt CPR treatment, during the natural course ofrepetitive CPR treatment, and/or during ventilations) while some of thedata after completion of CPR treatment is being collected and analyzedfor further confirmation of an initial determination of whether therhythm is shockable or not shockable. As discussed herein, confirmationof an initial determination of shockability is sometimes referred to asa reconfirmation mode which may allow for filtered, eliminated orotherwise reduced CPR artifact in the signal during analysis, but it maypose a potential danger to the patient depending on how long the CPRtreatment is halted. Thus, if the evaluation of clauses against timesegments of the data is successful in determining the state of thepatient after a relatively short amount of time, e.g., less than 6seconds, the CPR treatment can resume relatively quickly, reducing riskto the patient. By detecting the exact moment at which the rescuerceases chest compressions utilizing the proximity sensor, the timeperiod in which CPR treatment is halted for the reconfirmation mode isminimized.

In some implementations, some or all of the ECG data being acquired isstored during a reconfirmation mode of a CPR treatment, when ECGanalysis occurs during CPR treatment and during a brief period after CPRtreatment. In reconfirmation mode, the CPR treatment may be temporarilyhalted so that the CPR treatment does not affect the signal beingacquired for confirming the recommendation of whether to administer adefibrillating shock. In some examples, the reconfirmation mode isterminated, and the caregiver is prompted to reconvene CPR treatment,when sufficient ECG data has been acquired.

With reference to FIG. 15, a specific example of a reconfirmation modeis provided. FIG. 15 provides a diagram representing a technique 320 fordetermining whether a patient is in a shockable or non-shockable statebased on an ECG signal measured from the patient, according to either avoting process or whether a high accuracy clause is met before thevoting process is complete. As described above, a high accuracy clauseis a clause that exhibits a high predictive certainty based on PPV(positive predictable values) and/or NPV (negative predictive value).The technique 320 can be implemented as functionality of adefibrillator, e.g., the AED 10 shown in FIG. 1A.

The technique 320 includes two modes. The first mode 322, which is anoptional mode, sometimes referred to as “Continuous Analysis Mode”(CAM), includes a CPR window 324 in which measurements are taken whileCPR (chest compressions) is being applied to the victim. During the CAMmode, it may be determined based on the ECG analysis that the patientmay or may not require a defibrillation shock, where such adetermination is to be confirmed by a hands-free period of ECG analysis.The second mode 326, sometimes referred to as “Reconfirmation AnalysisMode” (RAM), is performed during a CPR-free window 328, e.g., duringwhich time CPR (chest compressions) is not applied to the victim. Duringthe RAM mode, the initial determination made during the CAM mode isconfirmed or not confirmed. In some examples, the second mode 326 isentered into once the proximity detector sends a signal to the AED 10that the rescuer has removed his/her hands from the patient's chest. Insome examples, the application of CPR can interfere with detecting a“clean” ECG signal (e.g., a signal absent substantial noise induced bythe CPR treatment), so the second mode 326 can be used to detect aCPR-free signal. The technique 320 can alternate between the first mode322 and the second mode 326, e.g., during a rescue situation. In someexamples, the mode changes when the AED 10 detects that CPR has stoppedor started (e.g., by detecting that the motion associated with chestcompressions has stopped or started or through the use of the proximitydetector). In some examples, the mode changes when the AED 10 providesan instruction to a rescuer (e.g., using an output device such as adisplay or audio output device) to stop or start CPR.

In the first mode 322, an analysis of successive segments 330 a-c of anECG signal during CPR can be performed. For example, if any clauses usedfor ECG analysis during CPR are met by any of the segments 330 a-c, adecision (e.g., CAM decision) of whether the ECG signal represents ashockable or non-shockable rhythm is saved 332 (e.g., for latercomparison with an analysis during the CPR-free window to finalize thedetermination). The decision can be based, for example, on clausesapplied to the segments 330 a-c. Because analysis during CPR may be lessreliable than analysis made when CPR has stopped, the saved decision canbe confirmed in the second mode 326.

In the second mode 326, CPR is halted and, based on a signal from theproximity sensor, ECG signal segments 334 a-c can be analyzed absent anypotential noise from the CPR treatment. A first segment 334 a isanalyzed, e.g., by applying 336 high accuracy clauses to the segment 334a. If the high accuracy clause is met, e.g., by indicating a shockableor non-shockable rhythm, then a decision of a shockable or non-shockablerhythm has been reached 338 and further analysis need not be undertaken.If not, other normal accuracy clauses can be applied 340 to the segment334 a. If one of the other clauses (e.g., a normal accuracy clause) issatisfied by the segment and that clause indicates the same result(e.g., a RAM decision indicating a shockable rhythm or non-shockablerhythm) as was indicated in the saved decision 332 (e.g., CAM decision)of the first mode 322, then a decision of a shockable or non-shockablerhythm has been reached 342. Put another way, because the results match,the matching result (e.g., between the CAM decision and the RAMdecision) can be used as the final decision. However, if the othernormal accuracy clause(s) indicate a different result as the saveddecision, then the result of the other normal accuracy clause(s) issaved 344 and the technique 320 proceeds to analysis of a second segment334 b.

During analysis of the second segment 334 b, high accuracy clauses canagain be applied 346. If a high accuracy clause is met, e.g., byindicating a shockable or non-shockable rhythm, then a decision of ashockable or non-shockable rhythm has been reached 348 without furtherprocessing required. If not, other clauses can be applied 350 to thesegment 334 b. If another clause (e.g., a normal accuracy clause)indicates the same result (e.g., a shockable rhythm or non-shockablerhythm) as the saved result 344 of the analysis of the first segment 334a, then a decision of a shockable or non-shockable rhythm has beenreached 352. If the other normal accuracy clause(s) indicate a differentresult as the saved result 344, then the result of the other normalaccuracy clause(s) is saved 354 and the technique 320 proceeds toanalysis of a third segment 334 c.

During analysis of the third segment 334 c, high accuracy clauses areagain applied 356. If a high accuracy clause is met, e.g., by indicatinga shockable or non-shockable rhythm, then a decision of a shockable ornon-shockable rhythm has been reached 358. If not, other normal accuracyclauses can be applied 360 to the segment 334 c, and a “2 out of 3” votecan occur. If another clause (e.g., a normal accuracy clause) indicatesthe same result (e.g., a shockable rhythm or non-shockable rhythm) aseither of the saved result 344 of the analysis of the first segment 334a or the saved result 354 of the analysis of the second segment 334 b,then a decision of a shockable or non-shockable rhythm has been reached364. Put another way, when two of the three results match, thosematching results (e.g., shockable or non-shockable) is used as thedecision of whether the patient is in a shockable or non-shockablestate. Additional examples of reconfirmation analysis are provided inUnited States Patent Application Publication No. 2017/0225001, which ishereby incorporated by reference.

FIG. 16 shows a flowchart of an example process 420 for identifying apresence of a shockable rhythm in ECG data. The process 420 can beimplemented, for example, by the MPU 212 shown in FIG. 12, and appliedto ECG data.

The process 420 includes receiving 422 data representing an ECG signalof a patient e.g., while the patient is undergoing rescue treatment. Theprocess 420 includes processing 424 a variable-length time segment ofthe ECG signal comprising an initial time period of between 0.1 secondand approximately 3 seconds. The processing includes identifying 426whether an interruption in chest compressions has occurred, e.g., byprocessing signals produced from at least one of an ECG electrode and amotion sensor. The processing includes analyzing 428 the variable-lengthtime segment of the ECG signal during the chest compression interruptionaccording to an initial rule set based on the initial time period. Theanalysis can be used to determine whether an ECG rhythm represented bythe ECG signal is shockable or non-shockable. In some examples, theinitial rule set includes one or more clauses representing constraintson one or more features of the ECG signal, each of the one or morefeatures of the ECG signal representing a characteristic of a waveformof the ECG signal within the processed time segment.

The processing includes, based on the initial rule set, determining 430whether the ECG rhythm represented by the ECG signal is shockable ornon-shockable or whether to extend the variable-length time segment forfurther analysis (e.g., if no accurate determination can be made usingthe initial time period). The processing includes generating 432 anoutput based on the determination of whether the ECG rhythm representedby the ECG signal is shockable or non-shockable. The process 420includes providing 434 an output based on the determination, e.g., byusing an output circuit or output module (e.g., output screen, audiocircuit, etc.).

As discussed herein, in the interest of determining whether an ECGrhythm represented by an ECG signal is shockable or non-shockable asquickly as possible, it may be desirable for gaps or interruptions inchest compressions to be analyzed as quickly and efficiently aspossible. Accordingly, the use of a proximity detector to determine theexact moment in which the rescuer removes his/her hands from thepatient's chest is beneficial. At any point whenever chest compressionshave ceased, even for a short period, an ECG analysis to determinewhether a rhythm is shockable or non-shockable, or to determine if moretime is needed, may be appropriate. In some instances, interruptions inchest compressions may be fairly short (e.g., less than approximately 3seconds). For instance, the rescuer may be inclined to readjust his/herposition, switch roles with another rescuer, be distracted, slightlyfatigued or may otherwise pause chest compressions. For such cases,since it is indeterminate as to when chest compression will recommence,it may be advantageous for the system to begin its rhythm analysisimmediately, so that minimal time for determining the cardiac state ofthe patient is wasted. In some instances, the time period of chestcompression interruption may be substantial (e.g., greater than 12-15seconds). For example, the rescuer may be instructed to stop CPR chestcompressions and wait for the defibrillating system to perform an ECGanalysis, the rescuer may switch to another resuscitation activityaltogether, such as ventilation, etc. In such cases, the ECG analysismay run its regular course.

For various implementations, as discussed above, the defibrillatorsystem may be configured to begin ECG analysis as soon as it identifiesan interruption in chest compressions being administered to the patient,or shortly thereafter. The defibrillator system may track chestcompressions by any suitable method or technique. In someimplementations, the defibrillator system incorporates a motion sensor(e.g., accelerometer, velocity sensor, displacement sensor) at alocation where the rescuer is administering chest compressions, todetect the presence of the chest compressions. For example, anaccelerometer may be embedded in a chest compression sensor and therescuer may place the chest compression sensor between the patient'schest and his/her hands during CPR compressions. The accelerationsignals produced by the sensor may be processed accordingly. Such amotion sensor may further be used to sense the depth and rate of chestcompressions, so as to provide the rescuer with appropriate CPRfeedback. Various implementations where a determination of whether acardiac rhythm is shockable based only on time periods of the ECG signalduring which there has not been CPR chest compressions delivered aredescribed in U.S. Pat. No. 6,961,612, entitled “CPR Sensitive ECGAnalysis in an Automatic External Defibrillator,” which is herebyincorporated by reference in its entirety, and may be used inconjunction with systems and methods described herein. Alternatively, orin addition to such a motion detector, a proximity detector positionedat a location on a patient's chest at which chest compressions will bedelivered can be utilized to identify when chest compressions haveceased.

FIGS. 17A-17F depict illustrative implementations that includeschematics where the defibrillator system quickly identifies whether aninterruption in chest compressions has occurred and applies anappropriate analysis algorithm. In each implementation, the respectiveschematics show a period of time in which CPR chest compressions arebeing provided. During this CPR window, as described further herein, thedefibrillator system may optionally apply a continuous analysis advisoryfor whether a shockable or non-shockable rhythm is detected, whiletaking into account artifacts that arise through chest compressions.Such a continuous analysis advisory may include appropriate filtering,frequency-based analyses, and/or other suitable analysis techniques forproviding an indication of whether a rhythm represented by the ECGsignal is shockable or non-shockable. This indication may be used tomake a determination (subsequently or at the time of analysis) ofwhether a defibrillating shock should be applied. For example, thecontinuous analysis advisory may indicate that the ECG rhythm is likelyto be shockable, and such an indication may be subsequently confirmedvia a subsequent hands-free ECG analysis, where CPR chest compressionsare not occurring. In general, a hands-free ECG analysis may providemore accurate shock analysis than continuous ECG analysis duringcompressions. Examples of suitable continuous analysis advisoryalgorithms (while during compressions) that may be employed includethose described in U.S. Pat. No. 8,706,214, entitled “ECG RhythmAdvisory Method,” and U.S. Pat. No. 8,880,166, entitled “DefibrillatorDisplay,” each of which are hereby incorporated by reference in theirentirety.

As discussed above, to make a final determination of whether the ECGrhythm sensed from the patient is one where a defibrillating shockshould be applied, it may be necessary to stop chest compressions for abrief period to analyze a more clean ECG (e.g., without artifactsarising from CPR chest compression). Accordingly, the defibrillatingsystem may prompt the user to stop CPR, for example, via an audio and/orvisual prompting from the user interface of the defibrillator. If theuser acknowledges this prompting and interrupts the process of applyingCPR chest compressions, the system will then analyze the clean ECG(absent chest compressions) to determine whether a shockable ornon-shockable rhythm exists when the proximity detector providessufficient information to confirm a determination that the hands of therescuer have been removed from the patient's chest. However, the usermight not acknowledge the prompt to stop CPR (e.g., might not see/hear,or may ignore the prompting from the defibrillator) and continue chestcompressions. If the user continues chest compressions, despite theprompting to stop chest compressions, the system may continue to applythe continuous analysis advisory that takes into account chestcompression artifacts in the ECG. Though, once the user halts chestcompressions, the system may immediately or within a short period oftime switch the type of ECG analysis from the continuous analysisadvisory (with compressions) to a hands-free analysis mode (withoutcompressions), which is able to more accurately confirm whether ashockable or non-shockable rhythm exists.

As shown in FIG. 17A, when the defibrillator system determines thatchest compressions should cease in favor of analyzing 440 the ECG signalto determine whether a shock should be applied, an instructive prompt442 is issued for the rescuer to stop CPR and be hands-free from thepatient. In various implementations, the system may optionally pause fora short period of time before hands-free ECG analysis. This short pause444 may be preferable in some cases to ensure that the ECG signal issubstantially free of artifact, present or residual, having arisen fromthe chest compressions. In some embodiments, a proximity sensor ordetector may be used during this short pause 444 to confirm thatcompressions are not being provided to the patient. While the example ofFIG. 17A shows the short pause time before hands-free ECG analysis to beapproximately 1.5 seconds, any appropriate pause time may be employed,such as less than 2 seconds, less than 1.5 seconds, less than 1 second,less than 0.5 seconds, less than 0.2 seconds, less than 0.1 second, etc.In some implementations, while not shown in this figure, upon detectionof an interruption in chest compressions, the hands-free ECG analysisadvisory may be immediately employed.

FIG. 17B depicts an implementation where chest compressions are stopped446 even prior to when the instructive prompt is provided by the system.While it is not advisable to cease chest compressions prematurely, forvarious reasons, it is common for rescuers to do so. In such a case,while not shown in the figure, the system may prompt the rescuer tocontinue chest compressions or display an idle timer that shows how longthe rescuer has ceased compressions, up until the time when the systemdetermines that chest compressions should be interrupted for hands-freeanalysis to commence. The implementation of FIG. 17B still pauses for ashort period of time after the prompt to stop CPR, however, it can beappreciated that such a pause is not required. For example, when aninterruption in chest compressions is detected via information generatedby the proximity detector, for example, the system may automaticallyand/or immediately begin hands-free ECG analysis advisory without anysuch pause.

FIG. 17C shows an implementation where chest compressions are continuedfor a short time 448 (e.g., 1-2 seconds) beyond the time in which thesystem issues the instructive prompt to stop CPR. In this case, thesystem tracks the chest compressions up until the time when compressionsare ceased, optionally pauses for a short period of time (e.g.,approximately 1.5 seconds), and then begins hands-free ECG analysisadvisory in accordance with the present disclosure. As discussed above,the short pause in chest compressions may be confirmed using theproximity sensor/detector.

FIG. 17D depicts another implementation of an instance where chestcompressions are continued for a longer period 450 than that shown inFIG. 17C. Here, the system continues to track the chest compressions,and after a sufficiently long time period, the system then issues asubsequent instructive prompt reminding the rescuer to stop CPR. It canbe appreciated that the subsequent instructive prompt can be provided atany suitable time, which may be predetermined by an appropriate timeinterval. In this particular case, the system issues the subsequentprompt after approximately 3 seconds which, in some cases, may besimilar to an initial time period of ECG analysis. As further shown,when chest compressions are interrupted, the system optionally pausesfor a short time (e.g., approximately 1.5 seconds) when it is confirmedthat the hands are off the chest, and then commences hands-free ECGanalysis advisory.

FIG. 17E shows an implementation where chest compressions are continuedfor an even longer period of time 452. In this example, the systemissues the first prompt 454 instructing the user to stop chestcompressions, and then after a sufficiently long time interval 456(e.g., approximately 3 seconds), the system then issues a subsequentinstructive prompt 458 reminding the rescuer to stop CPR compressions.However, here, the system continues to sense chest compressions afterthe subsequent instructive prompt, resulting in further delay in thehands-free CPR analysis advisory. In various implementations, the ECGsignal is tracked according to short time segments (e.g., approximately3 seconds), and once the system identifies an interruption in chestcompressions, the hands-free CPR analysis advisory begins at the startof the next time segment. As shown more specifically in FIG. 17E, thesystem does not detect an interruption in chest compressions, forexample, via information generated from the proximity sensor/detector,until approximately 2 seconds after the most recent instructive promptto stop CPR compressions. The hands-free CPR analysis advisory thenbegins after the approximately 1 second that remains in the 3 secondinterval elapses. Though, for certain implementations, after thesubsequent instructive prompt, as soon as an interruption in chestcompressions has been determined, the system may immediately beginhands-free CPR analysis advisory, without the optional pause.

FIG. 17F depicts another illustrative implementation where nointerruption in CPR chest compressions is detected, despite multipleinstructive prompts 460, 462 to stop chest compressions. In such a case,because chest compressions remain uninterrupted, for example, asdetermined via the proximity sensor/detector, the hands-free CPRanalysis advisory is unable to be used. In this case, the continuousanalysis advisory algorithm (which accounts for chest compressionartifacts) is applied throughout the time in which chest compressionsare administered.

B. Defibrillator Charging

The AED 10 also includes a charging module, such as the defibrillatorpulse generator 24, that is configured to charge the AED. In someimplementations the AED 10 can be adaptively charged based on monitoredECG signals. For example, the defibrillator can be pre-charged only if ashockable rhythm is likely to exist as determined by analysis of themonitored ECG signals. In another example, the level of charge for thedevice can be determined and set based on the monitored ECG signals. Insome implementations, the method of charging (e.g., the rate of charge,time of charging relative to the resuscitation process) can be variedbased on the monitored ECG signals in an effort to conserve power. Forexample, if time allows, a capacitor may be charged more slowly than itnormally would in order to conserve power, but still ensure that thecapacitor will reach its full charge just as the defibrillator is neededby the rescuer. An early identification of shockable rhythms, as may befacilitated by the technology described herein, may be used indetermining the method of charging. For example, a fast charging processcan be triggered upon identification of a shockable rhythm, therebyfurther reducing potentially life-threatening delays in administering ashock. On the other hand, if a shockable rhythm is not detected, the AED10 can be charged more slowly in order to achieve power savings. Or, ifit appears that an ECG rhythm may be shockable, but is not yetconfirmed, the defibrillator may preemptively begin charging in case therhythm does turn out to be shockable. This feature may be useful whenECG analysis occurs during chest compressions or during reconfirmationmode, where a short time period of analysis after chest compressions isused to confirm the existence of a shockable rhythm that had beendetected during chest compressions. In such a case, the defibrillatormay begin charging during the administration of chest compressions sothat the defibrillator is readily able to deliver a shock once thepresence of a shockable rhythm is confirmed. Alternatively, thedefibrillator may begin charging based on a signal from the proximitysensor indicating that the rescuer has ceased chest compressions, forexample, during the reconfirmation period. Further details ofdefibrillator charging are described in United States Patent ApplicationPublication Nos. 2016/0220833 and 2017/0225001, which are herebyincorporated by reference in their entirety.

C. Calculating AMSA During Chest Compression Pauses

Changes or trends in spectral frequency (e.g., amplitude spectral area(AMSA), FFT) may be used in evaluating the likelihood that an electricalshock will lead to a successful therapeutic result (e.g.,defibrillation). For example, when the AMSA or other frequency-baseddata is greater than a certain threshold, the percentage of shocksuccess can be sufficiently high such that a caregiver or medicalapparatus can make a decision to administer an electrical shock.Alternatively, for relatively low values of AMSA or otherfrequency-based data, observed changes in frequency-based data can be asubstantial contributor to the overall percentage of shock success.Changes or trends in spectral frequency of an ECG can provide furtherinformation (in addition to the actual values of the spectral frequencyanalysis), which can beneficially lead to a therapeutic shock at anearlier time, for example, as compared to a case where only the actualvalues of the spectral frequency are taken into account. Accordingly, byimplementing systems and methods described herein, patients can be ableto receive life-saving therapies quickly and effectively. However, AMSAcalculations used to predict the likelihood of shock success are muchmore reliable during pauses in chest compressions. Therefore, aproximity sensor may be utilized to detect when the hands of the rescuerhave been removed from the patient's chest such that AMSA or otherfrequency-based data may be calculated, and the likelihood of shocksuccess may be more reliably determined.

With reference to FIG. 18, an example of where AMSA calculations weremade during pauses in chest compressions are illustrated. As discussedabove, the pauses in chest compressions may be determined through theuse of a proximity sensor positioned at or nearby a location on thepatient's chest where chest compressions are delivered. Morespecifically, FIG. 18 is an example of a graphical representation 500that can be displayed by a patient monitoring and/or treatment device.The example graphical representation 500 includes a parallel display ofan ECG signal 552 a, AMSA 552 b, corresponding to the ECG signal, and aCPR signal 552 c, recorded in parallel with the ECG signal. Line 552 bis represented as AMSA values computed periodically throughout theallotted time period, including during cardiac treatment (e.g., CPR).

The example graphical representation 500 illustrates AMSA 552 b in apatient suffering of VF, being treated with CPR according to standardprotocol (e.g., completing 2 minutes of CPR between each singledefibrillation attempt). In the illustrated example, two defibrillationshocks were delivered to the patient. The first shock, which failed, wasdelivered at around 10 minutes and the second shock, which succeeded,was delivered at around 13 minutes. The average AMSA value measured overa period of few seconds prior to the first shock (AMSA₁) was about 4.9mVHz, which is below an early shock threshold, such as approximately 12mVHz, approximately 13 mVHz, approximately 14 mVHz, approximately 15mVHz, or another threshold value. The average AMSA value 158 measuredover a period of few seconds prior to the second shock (AMSA₂) was about8.6 mVHz. The general trend of AMSA 552 b over time illustrates agenerally increasing trend between AMSA₁ and AMSA_(2,) notably duringCPR pauses. Accordingly, it is advantageous to determine such CPR pausesusing a proximity detector such that useful values of AMSA can bereliably determined.

In this example, three points on the AMSA line 552 b are particularlyrelevant, corresponding to certain evaluation periods: points 554, 556and 558, which were calculated during CPR pauses to avoid compressionartifacts. In one example, the CPR pauses were detected using aproximity sensor as described hereinabove. These points representevaluation periods at which the combined AMSA value measurement (e.g.,mean or median value determined over a window of time) are below apredetermined value associated with defibrillation success, but thechange from the first recorded AMSA value AMSA₁ (4.9 mVHz) to each ofthese three points can be used as indicators of defibrillation success.For example, referring to point 556 (taken at a time when there is apause in CPR compressions, which can generally provide for more reliableAMSA values than when CPR compressions are being administered), therespective AMSA value is about 9 mVHz, which corresponds to a change inAMSA of approximately over 4 mVHz. Such a change in AMSA is indicativeof a relatively high likelihood of shock success, at least comparable orgreater than the AMSA value at point 558. Such data can indicate thatanalyzing AMSA in parallel with or in between CPR signals can assist arescuer in providing successful defibrillation therapy at time intervalsdifferent than the standard protocol, defining a personalized treatmentoptimized for each patient, which can be materially different fordifferent patients. For instance, as shown above, because the change inAMSA from the first recorded AMSA value AMSA₁ to point 556 issubstantial, the system can provide a recommendation and/or decision forthe patient to be treated with an electrical shock at a time (e.g.,point 556) prior to the standard treatment protocol, rather thanwithholding shock treatment until point 558.

If AMSA value is below the predetermined defibrillation threshold (e.g.,15 mVHz) AMSA value can be continuously monitored and the change in AMSAbetween times t₁and t₀ or t₂ and can be used to determine when and if adefibrillation shock can be delivered. For a majority of patients withlow initial AMSA (as illustrated in FIG. 18), CPR cannot be able togenerate an increase of AMSA to reach the early shock threshold, such asapproximately 12 mVHz, approximately 13 mVHz, approximately 14 mVHz,approximately 15 mVHz, or another threshold value. In someimplementations, an upward overall trend (e.g., linear, non-linear,average increase over time) in AMSA can be used as an indicator thatdefibrillation can be successful. For example, an absolute change inAMSA determined as the difference between an initial AMSA value and alater AMSA value can be calculated. The change in AMSA value over timecan be used in determining a probability of defibrillation success. Insome implementations, each unit increase in AMSA, can be associated to aparticular percentage increase of the odds of shock success. The upwardtrend in AMSA over time can be determined over any suitable time periodin which resuscitation and/or therapeutic activities are occurring. Insome cases, the upward trend can occur for a short, fleeting period,leading to a short interval of opportunity in which the administrationof a shock or other appropriate therapy is likely to be successful,despite a generally downward trend over a longer period. The change inAMSA, and, in particular the identification of an upward trend, can becalculated or otherwise determined via any suitable mathematical method.For example, the change in AMSA can be estimated based on calculating aslope of a line intersecting two or more AMSA points, by using apolynomial function, by implementing a non-linear function, calculatinga spline estimation, by determining the derivative, by using regressionanalysis, by applying interpolation techniques, and/or other methodsfamiliar to those of skill in the art.

In some implementations, a change in AMSA can be a more sensitiveindicator for shock success in patients with low initial AMSA and ametric derived from the change in AMSA can be useful to guide CPRefforts, including timing of shock delivery. In some implementations, atable or an odds ratio-AMSA range curve can be used to directly identifythe increase in defibrillation success for each mVHz change in AMSA.Additional details of the manner in which changes or trends in spectralfrequency (e.g., AMSA, FFT) can be used in evaluating the likelihoodthat an electrical shock will lead to a successful therapeutic result(e.g., defibrillation) are discussed in United States Patent ApplicationPublication No. 2017/0120063, which is hereby incorporated by referencein its entirety. Based on the above description, it is important todetermine a pause in chest compressions prior to calculating AMSA andusing the trend to provide an estimation of shock success. Accordingly,the pause in chest compressions can be determined by using a proximitysensor positioned on a patient's chest at a location where chestcompressions are delivered. The proximity sensor provides a signal tothe defibrillator that the rescuer has removed his/her hands from thechest of the patient. Thereafter, trends over particular time intervalscan calculated at the beginning and end of the time interval.

D. Detecting pauses in chest compressions to provide a ventilationindication

In yet another implementation, a proximity sensor may be utilized todetermine that the rescuer has removed his/her hands from the patient'schest and that compressions have stopped. Once the defibrillatorreceives such a signal from the proximity detector, the defibrillator isconfigured to provide at least one of an audible and/or visualindication to the user to begin ventilations either manually through theuse of a bag or by an automated ventilation system.

As an example, a common protocol employed by emergency services duringresuscitation is a 30:2 protocol, where 30 chest compressions areapplied for every 2 positive ventilation breaths. Thus, the system mayprovide an indication of the number of chest compressions that have beenapplied so as to guide/coach the user in applying ventilations at theappropriate time(s), and/or to coordinate timing of positive pressurebreaths provided by an automated ventilation system. For example, if a30:2 compressions to ventilations protocol is employed, the proximitysensor, either alone or in combination with a motion sensor as describedhereinabove, may be used to detect whether chest compressions areapplied. The system may further count the number of applied compressionsand then alert the rescuer to give breaths once the proximity detectorissues a signal indicating the chest compressions have ceased.

In some embodiments, it can be beneficial to time the CPR compressionssuch that the CPR compression does not occur at the same time as aventilation. In such cases where a positive pressure ventilation and achest compression are administered simultaneously, the sudden pressurebuild up within the thoracic cavity may be injurious. Accordingly, thesystem may time compressions provided by manual CPR compressions via theproximity sensor. Based on information from the proximity sensor, thesystem determines whether a timing for a ventilation overlaps with atiming for a CPR compression cycle and provides an indication to therescuer if a ventilation is being delivered during a compression cycleso the rescuer can delay either the compression or the ventilation sothat they do not overlap. Or, in some cases, when it is time to promptthe user to administer a positive pressure ventilation, the proximitysensor may be used to confirm that a chest compression is not occurringand then the appropriate prompt to give the positive pressure breath maybe given.

Many other implementations other than those described may be employed,and may be encompassed by the following claims.

The invention claimed is:
 1. A system for assisting a rescuer inperforming cardio-pulmonary resuscitation (CPR) on a patient, the systemcomprising: a proximity sensor configured to be positioned at a locationcorresponding to a location of a rescuer's hand when deliveringcompressions to a patient's chest, the proximity sensor configured toproduce a signal indicative of the rescuer's hands being released fromthe patient's chest; a medical device operatively coupled with theproximity sensor and configured to provide resuscitative treatment tothe patient; and a controller communicatively coupled with the medicaldevice and the proximity sensor, and the controller configured to:determine, based upon the signal from the proximity sensor, if therescuer's hands have been released from the patient's chest, and triggeran action by the medical device in response to a determination that therescuer's hands have been released from the patient's chest.
 2. Thesystem of claim 1, wherein the proximity sensor comprises at least oneof a capacitive sensor, an ultrasonic sensor, an E-field sensor, and alight emitter-receiver pair.
 3. The system of claim 2, wherein thedetermination that the rescuer's hands have been released from thepatient's chest is based on a measurement from the proximity sensor thatthe rescuer's hands are greater than 1 cm away from the patient's chest.4. The system of claim 1, wherein the medical device is a defibrillatorcomprising an electrical storage device capable of delivering atherapeutic pulse to a patient.
 5. The system of claim 4, wherein theaction is charging the electrical storage device of the defibrillator.6. The system of claim 1, further comprising at least one sensoroperatively connected to the controller for obtaining one or moreelectrocardiogram (ECG) signals from the patient.
 7. The system of claim6, wherein the controller is further configured to: determine, basedupon the signal from the proximity sensor, if the rescuer's hands are incontact with the patient's chest, analyze the one or more ECG signalsfrom the patient during delivery of chest compressions to the patient,and determine a desirability of a shock to the patient based on theanalysis of the one or more ECG signals during the delivery of chestcompressions of a CPR cycle.
 8. The system of claim 7, wherein theaction is an analysis of one or more ECG signals acquired in an absenceof chest compressions to reconfirm the desirability of the shock to thepatient, the absence of chest compressions being based on thedetermination of whether the rescuer's hands have been released from thepatient's chest.
 9. The system of claim 6, wherein the controller isconfigured to: perform at least one transformation of at least a portionof the one or more ECG signals from the patient into frequency domaindata based on the determination of whether the rescuer's hands have beenreleased from the patient's chest, determine a first frequency-basedvalue over a first evaluation period based on the at least onetransformation, determine a second frequency-based value representing atrend over a second evaluation period based on the at least onetransformation, determine a probability of therapeutic success based atleast in part on the first frequency-based value and the secondfrequency-based value, and provide an indication of the probability oftherapeutic success.
 10. The system of claim 9, wherein the firstfrequency-based value comprises an amplitude spectral area (AMSA) valueand the second frequency-based value comprises an AMSA trend.
 11. Thesystem of claim 1, wherein the medical device comprises a feedbackdevice operatively connected to the controller.
 12. The system of claim11, wherein the feedback device is configured to provide feedbackreceived from the controller to the rescuer regarding compressions. 13.The system of claim 11, wherein the action is providing an indicationvia the feedback device to provide ventilation to the patient.
 14. Thesystem of claim 13, wherein the indication is at least one of an audioindication and a visual indication.
 15. A method for assisting a rescuerin performing cardio-pulmonary resuscitation (CPR) on a patient, themethod comprising: positioning a proximity sensor at a locationcorresponding to a location of a rescuer's hand when deliveringcompressions to a patient's chest; producing, with the proximity sensor,a signal indicative of the rescuer's hands being released from thepatient's chest; determining, based upon the signal from the proximitysensor, if the rescuer's hands have been released from the patient'schest; and triggering an action by a medical device in response to adetermination that the rescuer's hands have been released from thepatient's chest.
 16. The method of claim 15, further comprisingobtaining one or more electrocardiogram (ECG) signals from the patient.17. The method of claim 16, further comprising determining, based uponthe signal from the proximity sensor, if the rescuer's hands are incontact with the patient's chest, analyzing the one or more ECG signalsfrom the patient during delivery of chest compressions to the patient;and determining a desirability of a shock to the patient based on theanalysis of the one or more ECG signals during the delivery of chestcompressions of a CPR cycle.
 18. The method of claim 17, wherein theaction is an analysis of one or more ECG signals acquired in an absenceof chest compressions to reconfirm the desirability of the shock to thepatient, the absence of chest compressions being based on thedetermination of whether the rescuer's hands have been released from thepatient's chest.
 19. The method of claim 16, wherein the action is:performing at least one transformation of at least a portion of the oneor more ECG signals from the patient into frequency domain data based onthe determination of whether the rescuer's hands have been released fromthe patient's chest; determining a first frequency-based value over afirst evaluation period based on the at least one transformation;determining a second frequency-based value representing a trend over asecond evaluation period based on the at least one transformation;determining a probability of therapeutic success based at least in parton the first frequency-based value and the second frequency-based value;and providing an indication of the probability of therapeutic success.20. The method of claim 19, wherein the first frequency-based valuecomprises an amplitude spectral area (AMSA) value and the secondfrequency-based value comprises an AMSA trend.
 21. The method of claim15, wherein the action is providing an indication to ventilate thepatient.